For example, in a steering apparatus for applying a steering angle to steered wheels of an automobile as shown in FIG. 8 (except for special vehicles such as a forklift or the like, in general, to front wheels), movement of a steering shaft 2 that is rotated according to an operation of a steering wheel 1 is transmitted to an input shaft 6 of a steering gear unit 5 via universal joints 3 and 3 and an intermediate shaft 4. The steering gear unit 5 includes a pinion driven to be rotated by the input shaft 6, and a rack meshed with the pinion. When the pinion is rotated with the input shaft 6, the rack is displaced in an axial direction, a pair of tie rods 7 and 7 coupled to both of end portions thereof are pushed and pulled, and a desired steering angle is applied to the steered wheels.
A plurality of rack teeth are formed in a portion of one side surface in a radial direction of the rack that constitutes the steering gear unit 5 at equal intervals in the axial direction. When such a rack is manufactured by forming a plurality of rack teeth through cutting of a metal material, manufacturing costs are high, and also, it is difficult to secure strength and rigidity for the rack teeth. On the other hand, when the plurality of rack teeth are formed by plastically deforming the material, the time consumed in processing the rack teeth can be decreased to reduce manufacturing costs, and further, it is easy to secure strength and rigidity for the rack teeth because a metal structure of the obtained rack teeth becomes precise. In this way, the inventions disclosed in Patent Documents 1 to 2 are known in the related art as inventions that relate to a method of manufacturing a rack processed by plastic deformation of rack teeth.